1. Field of the Invention
This invention relates to an ink fountain apparatus for use with a printing press adapted to store always a predetermined amount of ink supplied by an ink supply unit in an ink fountain thereof.
2. Description of the Prior Art
As ink fountain apparatuses, there are publicly known, for example, those described in Japanese Laid-Open Utility Model Application Nos. SHO 64-1939 and SHO 63-18244.
The ink fountain apparatus shown in Japanese Laid-Open Utility Model Application No. SHO 64-1939 comprises an ink fountain located below a fountain roller; an ink nozzle mounted in the ink fountain so as to be oriented to the peripheral surface of the fountain roller; an ink supply conduit connecting the ink fountain with the ink nozzle; a pump mounted in the ink supply conduit; and an ink stirring conduit branched downstream of the pump in the ink supply conduit and connected to the bottom of the ink fountain, the arrangement being made such that the ink stored in the ink fountain can be supplied by the pump into the ink nozzle through the ink supply conduit, and as occasion demands, a stirring effect can be given to ink by circulating it through the ink stirring conduit.
Further, Japanese Laid Open Utility Model Application No. SHO 63-18244 discloses an ink tank apparatus wherein the ink stored in an ink tank is collected through the action of a screw, and the ink thus collected is supplied by a pump into an ink delivery nozzle mounted opposite to an ink supply roller through an ink supply conduit, and a surplus amount of ink is recovered into the ink tank.
It is known that pressure loss .DELTA.P which occurs when a fluid having a viscosity .mu. is pressurized by a pump and transferred in a laminar flow through a pipe having a diameter "D" and a length "l" is represented by a formula .DELTA.P=128 .mu.lQ/.pi.D.sup.4 wherein Q is the flow rate of the fluid. Stating in brief, it is known that the higher the viscosity of the fluid, and the longer the length of the pipe, and further the more the flow rate of the fluid, the higher the pressure loss becomes thus rendering the fluid transfer difficult, whilst the larger the pipe diameter, the lower the pressure loss becomes.
In the above-mentioned ink fountain apparatuses, however, all passages through which the ink stored in an ink reservoir section is transferred by a pump and which extend between the ink reservoir section and the pump and also between the pump and an ink receiving section are formed by conduits having small diameters. Therefore, in order to ensure that a sufficient amount of ink is delivered by the nozzle, the provision of a pump having a comparatively large capacity capable of covering such a pressure loss in the pipe and a driven unit having a relatively large capacity was required, and also it was necessary to provide a comparatively large space for installation of pipings. Therefore, it was difficult to make the configuration of the above-mentioned ink fountain apparatus small-sized and compact.
Still further, the use of a pump in the condition that relatively high pressure losses occur has expedited damage of the pump, thus reducing the life-time thereof.
Whilst, as ink fountains, there are publicly known those described in Japanese Laid-Open Patent Application Nos. SHO 35-12862, SHO 39-5717 and SHO 59-393.
These publicly known ink fountains are arranged such that the ink supplied from an ink tank provided separately in an amount more than the actual consumption is caused to overflow from an intermediate partition so that a pre-determined amount of ink can always be stored therein. And, the level of the ink stored in the ink fountain is arranged to be kept lower than end shafts of a roller which is rotated while it is partially immersed in the ink in the ink fountain.
As described above, since the level of the ink stored in the prior art ink fountain is arranged to be kept lower than end shafts of a roller which is rotatively driven while it is partially immersed in the ink in the ink fountain, only less than the half of the peripheral surface of the above-mentioned roller is immersed in the ink in the ink fountain. Therefore, the ink which is desposited on the peripheral surface of the roller while it is partially immersed in ink and which comes out of the surface of ink, as the roller is rotated, tends to drop from the peripheral surface owing to mechanical vibrations, etc. during its passage to a downstream roller which is engaged with or located close to the fountain roller. This caused fluctuations in the amount of ink to be supplied to the above-mentioned downstream roller so that uniform quality of printing could not be achieved. Further, in worst cases, a sufficient amount of ink required for printing could not be supplied. Such difficulties have frequently occurred when dampening water made ingress into the ink supply passage in lithography using a highly viscous ink and dampening water.